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The study investigated the effect of nickel content on the microstructure and mechanical properties of Cu–12Al-xNi alloys prepared using powder metallurgy. The results indicated that the alloys investigated consisted of α-Cu and γ 2 (Al 4 Cu 9), containing less than 4 wt% Ni content. The α-Cu phase gradually increased, while the γ 2 (Al 4 Cu 9) phase gradually decreased as the sintering temperature increased. Both the strength and hardness of the alloy thus reduced. When the Ni content increased above 4 wt%, the NiAl phase precipitated at the grain boundaries, which resulted in an increase in the strength of the alloy. Additionally, the tensile strength reached a maximum of 390 MPa when the Ni content reached 6 wt%. The decrease in the tensile strength for higher Ni content was attributed to the formation of a NiAl phase network. And the addition of nickel did not significantly alter the sintering density of the alloy. The mechanisms of microstructure evolution and strengthening mechanisms were investigated and discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A computational materials design to develop novel single crystal superalloys. • Achieving design balance of multi-objective properties. • Comprehensive design through DFT, empirical models, CALPHAD, and machine learning. • 12 alloys selected from 779,625 alloys in trade-offs between different factors. The computational materials design is performed to develop novel single crystal superalloys with balance of multi-objective properties. The entire design process is carried out by materials computation from systems selection to composition determination. The design rules are proposed to optimize compositions of Ni-based single crystal superalloys for materials characteristics, using first-principles calculations, CALPHAD calculations, theoretical models, and machine learning. By first-principles calculations, the effect of alloying elements on structural, elastic, electronic properties of Ni 3 Al are investigated and the Ni-Al-V-Cr-Nb-Mo-Ta-W-Re systems are determ5ined. Application of theoretical models and CALPHAD calculations allows the large materials exploring space to become narrow, based on materials design criterion: microstructure, density, castability, and processability. The creep resistance of remained alloys is estimated by using machine learning and creep merit index. There are 12 alloys selected from 779,625 composition combinations, reaching the balance of multiple design properties. With comparing to commercial superalloys, the selected alloy has excellent performance in trade-offs between different factors, specifically prominent in the aspect of Cr-Al space of oxidation resistance. This design procedure is expected to reduce excessive consumption of cost and time in the process of trial-and-error testing, providing a guide on developing potential Ni-based superalloys systems. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) composed of Ti, Zr, Hf, and Nb have emerged as promising materials for high-temperature aerospace applications due to their exceptional balance of strength and toughness, coupled with a reduced density and softening resistance. This study delves into the influence of alloy composition on the mechanical properties, a pivotal aspect in the design of RHEAs. We investigate a series of Ti 48-x Zr x Hf 26 Nb 26 (x = 14, 18, 22, 26, 30, 34) alloys, prepared through suction casting and homogenization treatments. The phases, microstructure, and fracture morphology of these alloys are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), subsequent tensile tests provide insights into the strength and elongation characteristics of alloys. The homogenized alloys consistently exhibit one BCC phase with equiaxed grains, whereas the fracture mode shifts from intergranular to transgranular, and return to intergranular as the Zr content increases. Experimental results reveal an asymmetry mechanical behavior, alloys with higher Ti content display superior toughness (elongation 17.83 % for Ti = 34 at%) compared to those with higher Zr content (elongation 16.05 % for Zr = 34 at%). Among them, the Ti 22 Zr 26 Hf 26 Nb 26 alloy achieves the peak tensile strength of 695.25 MPa, indicating an inverse relationship between strength and toughness. Solid-solution strengthening and chemical short-range orderings emerge as the predominant contributors to the overall strength of the TiZrHfNb alloys. To gain a deeper understanding of the mechanical behavior at the atomic scale, we performed first-principles calculations to investigate the elastic properties and charge density of Ti 48-x Zr x Hf 26 Nb 26 alloys in the BCC structure. These calculations shed light on the underlying mechanisms governing the strength and toughness behavior. The present work offers valuable insights into the design of mechanical properties of TiZrHfNb RHEAs, serving as a paradigm for future materials development in this field. • Microstructure and mechanical behaviors of TiZrHfNb RHEAs are investigated. • The asymmetrical tensile strength and elongation exhibited, alloys with a lower content of Zr have superior toughness. • DFT calculations of the elastic modulus and charge density are performed to elucidate the experimental findings. • CSROs and solid-solution strengthening significantly contribute to tensile strength, the peak value reaching 695.25 MPa. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy composition design problem has always been a fundamental task for growing demands in intended applications. In this paper, we establish a nickel-based polycrystalline superalloy composition design framework to excavate novel alloys with superior properties efficiently and comprehensively. First, we establish a model of creep resistance with respect to composition proportions with little data knowledge and computational effort based on the Gaussian process regression. Then, we solve the constrained multi-objective nickel-based superalloy composition design problem, aiming at maximizing the creep resistance while minimizing the alloy cost, by meta-heuristic non-dominated sorting genetic algorithm II efficiently, which enables fast searching rather than simply ranking in large-scale solution space. Pareto fronts containing optimal candidate alloys where the trade-off between creep resistance and alloy cost is fully considered are obtained. Finally, we filter the unqualified candidate alloys that dissatisfy the phase fraction of superalloy on several Pareto fronts based on some screening indicators computed by JMatPro software, and a set of well-performed alloys with high creep resistance and low alloy cost is obtained. • Establishing property-composition model with little data knowledge and computational effort. • Building creep resistance model based on Gaussian process regression. • Solving constrained nickel-based superalloy composition design problem by intelligent searching. • Simultaneously maximizing creep resistance and minimizing alloy cost based on NSGA-II. • Pareto fronts fully considering the trade-off between optimal properties are obtained. [Display omitted] [ABSTRACT FROM AUTHOR]

The phase field model for multicomponent alloys are usually coupled with the thermodynamic database. But it will take much time to solve the quasi phase equilibrium equations. In order to reduce such time and keep the enough accuracy, we develop a new model to predict the quasi phase equilibrium based on the machine learning method. As an example, the quasi phase equilibrium during the isothermal solidification of Al-Cu-Mg alloy is studied in detail. A neural network model with 3 inputs, 4 outputs and a hidden layer of 150 nodes is constructed. The "training data" are prepared by solving the quasi phase equilibrium equations with least square method. The neural network model is trained by different amount of data set, which can fully cover the ranges of all the variables. The accuracy and performance of the neural network model are discussed in detail. Its high accuracy and fast speed demonstrated that this will be a convenient method to acquire the quasi phase equilibrium data in phase field model for multicomponent alloys. [ABSTRACT FROM AUTHOR]